For example, semiconductor devices, liquid-crystal display devices, or the like are manufactured using a projection exposure apparatus for projecting a pattern of a mask (reticle, photo-mask, or the like) through a projection optical system onto a plate (glass plate, semiconductor wafer, or the like) coated with a resist. The conventional projection exposure apparatus frequently used was one (stepper) for implementing one-shot exposure of a pattern of a reticle in each of shot areas on a plate by the step-and-repeat method. Recently suggested is the projection exposure apparatus of the step-and-scan method having a plurality of small partial projection optical systems with a magnification of 1× arranged in two or more rows at a predetermined interval along a scanning direction, instead of one large projection optical system, and adapted to project patterns of a mask onto a plate through the respective partial projection optical systems to effect exposure thereof, while scanning the mask and the plate relative thereto (cf. Japanese Patent Application No. 5-161588).